A Short History of CAE Cars

By: Boom San Agustin

For half a century the air-powered locomotive was a serious contender for the top spot in transportation because of its obvious advantages: simplicity, safety, economy, and cleanliness. Air engines were commercially available and used routinely, first as metropolitan street transit and later for haulage in mines.

The term "air engine" disappeared from engineering textbooks after the 1930s and the second world war. Gas engines had been perfected, the oil industry was established, and gas was cheap.

Serious interest in air cars was rekindled by the energy glitches of the 1970s. Dozens of inventors have patented designs for hybrid, closed cycle, and self-fueling air cars, as well as conversions for existing engines and designs for air cars meant to stop at air stations for refueling.

The Pneumatic Railway, 1880s to today

Like modern electric subway trains, the power supply was provided continuously by a pipeline laid along the track. This concept was not practical at the time it was invented (1820s) because the materials were not available to make it work reliably. A modern version appeared in Brazil in the 1980s, invented by Oskar H. W. Coester, and developed by Aeromovel Global Corp.

The Mekarski Compressed Air Locomotive, 1886-1900

The Mekarski air engine was used for street transit. It was a single-stage engine (air expanded in one piston then exhausted) and represented an advance in air engine technology that made air cars feasible: the air was reheated after leaving the tank and before entering the engine. The reheater was a hot water tank through which the compressed air bubbled in direct contact with the water, picking up hot water vapor which improved the engine's range-between-fill-ups.

The Hardie Compressed Air Locomotive, 1892-1900

Robert Hardie's air engine was a going concern in street transit in New York City. Air car advocate General Herman Haupt, a civil engineer, wrote extensively about the advantages of air cars, using the Hardie engine as his source material and providing much of the impetus for the New York experiment to gain support and succeed. The engine was a one-stage expansion engine using a more advanced type of reheating than the Mekarski engine. One of its new features was regenerative braking. By using the engine as a compressor during deceleration, air and heat were added to the tanks, increasing the range between fill-ups. A 1500 horsepower steam-powered air compressor station was built in New York City to supply the Hardie compressed air locomotives and the Hoadley-Knight pneumatic locomotives.

The Hoadley-Knight Compressed Air Locomotive, 1896-1900

The Hoadley-Knight system was the first air powered transit locomotive that incorporated a two-stage engine. It was beginning to be recognized that the longer you keep the air in the engine, the more time it has to absorb the heat that increases its range-between-fill-ups. Hoadley and Knight were also supporters of Nikola Tesla's disc turbine, for which they formed a propulsion company that didn't get off the ground.

The H. K. Porter Compound Air Locomotives, 1896-1930

Inventor Charles B. Hodges became the first and only air car inventor in history to see his invention become a lasting commercial success. His engine was two-stage and employed an interheater between the two piston stages to warm the partially expanded compressed air with the surrounding atmosphere. A substantial gain in range-between-fill-ups was thus proven attainable with no cost for the extra fuel, which was provided by the sun. The H. K. Porter Company in Pittsburgh sold hundreds of these locomotives to coal-mining companies in the eastern U.S. With the hopeful days of air powered street transit over, the compressed air locomotive became a standard fixture in coal mines around the world because it created no heat or spark and was therefore invaluable in gassy mines where explosions were always a danger with electric or gas engines.

The European Three-Stage Air Locomotive, 1912-1930

Hodges' patents were improved upon by European engineers who increased the number of expansion stages to three and used interheaters before all three stages. The coal mines of France and Germany and other countries such as Belgium were swarming with these locomotives, which increased their range-between-fill-ups 60% by the addition of ambient heat. It might have become obvious to the powers-that-be that these upstarts were a threat to the petroleum takeover that was well under way in the transportation industry; after world war two the term "air engine" was never used in compressed air textbooks and air powered locomotives, if used at all, were usually equipped with standard, inefficient air motors.

The German Diesel-Pneumatic Hybrid Locomotive, 1930

Just before technical journals stopped reporting on compressed air locomotives, they carried stories on a 1200 horsepower full-size above-ground locomotive that had been developed in Germany. An on-board compressor was run by a diesel engine, and the air engine drove the locomotive's wheels. Waste heat from the diesel engine was transferred to the air engine where it became fuel again. By conserving heat in this way, the train's range-between-fill-ups was increased 26%. A modern train engineer tells me that all train engines these days are hybrids: diesel-electric. And we are supposed to consider the Toyota Prius a miracle of modern invention?

Terry Miller, the Father of the Modern Air Car Movement

In 1979, Terry Miller set out to design a spring-powered car and determined that compressed air, being a spring that doesn't break or wear out, was the perfect energy-storing medium. From there he developed his Air Car One, which he built for $1500 and patented. He showed his air car from coast to coast and then went on to other things. In 1993 he picked up his air car project again with the help of Toby Butterfield of Joplin, Missouri. They developed the Spirit of Joplin air car with parts mostly donated by manufacturers. Terry's air engines demonstrated the feasibility of building air engines with off-the-shelf parts on a small budget. His engines used up to four consecutive stages to expand the same air over and over. They ran at a low speed so there was plenty of time for ambient heat to enter the system and the possibility of low-tech developers to build engines cheaply at home. Terry was instrumental in educating the founder of Pneumatic Options on air car fundamentals. Terry's greatest contribution--and what makes him an air car advocate, not just another inventor--was that he published and made easily available the complete details on how to build an engine like his. No other inventor has done this. Shortly before his death in 1997, Terry Miller gave all rights to his invention to his daughter and to Toby Butterfield. Mr. Butterfield died in 2002.

Guy Negre and MDI

Currently a French inventor named Guy Negre is building an organization to market his air car designs in several countries. A web search for air cars will turn up hundreds of references to his company, Moteur Developpment International (MDI). His website is at www.mdi.lu. Mr. Negre holds patents on his unique air engine in several countries. Plans are underway to build air car factories in Mexico, South Africa, Spain and other countries. We wish him success and encourage you to visit his website (or one of his licensees in Spain, Portugal, and Great Britain, theaircar.com) and support his good work.

C. J. Marquand's Air Car Engine

Dr. Marquand has taken the highly commendable step of incorporating heat pipes into his air engine design for the recovery of compression heat. He also plans to use regenerative braking. It is not clear whether his engine has been tested in a car yet. Professor Marquand is a scientist with a number of published research articles to his credit. For further information contact: C. J. Marquand or H. R. Ditmore, Dept. of Technology & Design, Univ. of Westminster, 115 New Cavendish St., London W1M 8JS, Tel. 0170 911 5000.

Tsu-Chin Tsao's Hybrid Air Engine for Cars

Tsu-Chin Tsao is a distinguished professor of mechanical and aerospace engineering at UCLA. He has invented a camless gasoline engine that does not idle; it uses compressed air to start the car, and when the air is gone the engine runs on gasoline. During deceleration, braking energy operates a compressor to fill the air tank for the next start. This brings to mind Buckminster Fuller's reminder in his magnum opus Critical Path, wherein he tells us how many horses (as in horsepower) could be jumping up and down going nowhere for all the gasoline being pointlessly burned by cars sitting at red lights at any given time. We have nothing but admiration and respect for Professor Tsao's serious step in a perfectly good direction, and apparently Ford Motor Company is in agreement: they are working with Tsao's team to look into the viability of putting a pneumatic hybrid on the road to compete with the Toyota Prius and other electric hybrids. The pneumatic hybrid is expected to save 64% in city driving and 12% on the highway.